Water absorbent resins are used owing to their absorbing property, water retaining property and gelling ability, in various fields, for example in absorbent articles such as paper diapers, incontinence pads, sanitary napkins and breast milk pads, and in drip absorbents, freshness preservatives, sheets for pets, excretion treatment agents, waste blood gelling agents, etc. However, while absorbent resins are excellent in the ability to absorb and retain urine, blood, body fluids, menstrual blood and the like, they can hardly show deodorant function. Therefore, since such liquids as urine, blood and body fluids have unpleasant characteristic odors and, further, are apt to readily rot under the influence of air and/or bacteria to give off offensive odors due to decay, the advent of a material capable of producing both absorbent and deodorant effects has been awaited from a hygienic viewpoint.
As means of satisfying both these requirements, the following have been proposed, among others: a mixture of an absorbent resin in powder form and zeolite in powder form (Japanese Kokai Publication Sho-57-25813, Sho-59-179114 and Sho-59-189854), a composition comprising active carbon coated with an absorbent resin (Japanese Kokoku Publication Sho-56-31425), a composition comprising an absorbent resin and an antimicrobial agent (Japanese Kokai Publication Hei-03-14867) and like compositions to be applied in absorbent articles; and an absorbent material prepared by admixing a zeolite slurry with a polymerization solution prior to polymerization and, after effecting polymerization, spraying the reaction mixture to a nonwoven fabric, followed by drying (Japanese Kokai Publication Hei-02-84957).
However, when these compositions are applied to absorbent articles, the deodorant effect obtained is not always satisfactory. That is to say, in the case of the mixture of an absorbent resin and zeolite, body fluids such as urine, blood, body fluid, menstrual blood is mostly absorbed and retained by the absorbent resin, since zeolite has little absorbent function. Therefore, in spite of the fact that the body fluid occurring within the absorbent resin is an odor source, the deodorant component zeolite exists apart from the odor source. This is presumably the reason why the deodorant effect cannot be produced to a satisfactory extent. Furthermore, the mixture of an absorbent resin and zeolite powder, when given vibrations or shock, may possibly separate into both components or, when applied to absorbent articles, may possibly allow localization of the absorbent resin and, therefore, of zeolite, with the result that the deodorant effect can be produced only to an unsatisfactory extent. For the production of a much better deodorant effect, it is desirable that the deodorant component should be disposed in contact with the body fluid odor source.
As for the composition comprising active carbon coated with an absorbent resin, active carbon itself is scanty in deodorant effect and, in addition, there is a problem that only limited kinds of odors can be adsorbed.
As regards the composition comprising an absorbent resin and an antimicrobial agent, those containing certain kinds of antimicrobial agents are effective to a certain extent in preventing bacteria and the like from causing decay but are scarcely effective against the characteristic odors intrinsic to body fluids itself. In addition, it is a draw back of such composition that no effect can be observed at all against those odors which result from the oxidative action of air.
Finally, a problem of the absorbent material prepared by admixing a zeolite slurry with a polymerization solution prior to polymerization and, after effecting polymerization, spraying the reaction mixture to a nonwoven fabric, followed by drying is that since the polymerization is carried out after dispersing zeolite in the polymerization solution, low-molecular-weight polymerizable monomers are adsorbed on pore inside surfaces of zeolite particles and thereafter polymerized to block up the pores and thus decrease the deodorant effect.